Propeller Nicks - Repair or let be ??

[Denis17]

Hi everyone,

We all know that manufacturers and training manuals emphasize the need to blend out stress riser type propeller nicks that occur when operating in rough environments. However, in certain cases nicks are so common that blending them out regularly would remove considerable blade material.

Do you find it important to always blend out propellers in accordance with manufacturer instructions ?
Have you ever heard of propeller failures caused by stress rising nicks ?

Please share your personal opinion based on field experience and standard industry practices.

[AirFrame]

...blending them out regularly would remove considerable blade material.

A failure due to a stress riser will also remove considerable blade material. Best to do it on the ground when you're not moving.

I've always blended out nicks in my prop.

[PilotDAR]

Have you ever heard of propeller failures caused by stress rising nicks ?

Yes, two. One having been experienced by a participant of AvCanada - 'his story to tell, not mine. The other, a floatplane friend who lost a few inches of tip on his 180 prop. The engine mount was damaged by the resulting vibration, but he made it home - sort of safely....

I advocate prevention, rather than the hope of repair for propellers. Yes, nicks can be dressed out, and tips reshaped, but to the manufacturer's limit, which may not be as much as one hopes for. In my junior years, I near scrapped a 182 prop by picking up some gravel at Maple airport. Leavens saved the blades, but that was it for them, no more tolerance for future damage.

Later I bought my 150. I got the McCauley manual, and made the measurements of the blades, there was not a lot left for future repair. The blades were okay, just not lots left if I was hard on them. So I was determined to be really careful with the prop. 34 years and 3000 hours later, I've had to dress out one small nick, and otherwise sand smooth the leading edge during annual inspections. The prop still meets the McCauley measurements with reserve. There are a few worthy tricks to prevent prop blade damage, they're worth knowing.

I'm intolerant of pilots who taxi light nosewheel planes around with the elevator limp, hold the nose high with up elevator. Nosewheel Cessnas respond well to being taxied with 15 flap extended, the changed airflow over the tail, combined with the up elevator, lifts the prop noticeably off the surface. And really watch out where you do runups, of course, with the elevator held nose up. No full power the brakes off for takeoff, add power on the roll, holding the nose up.

'Think I'm anal about this? Yup! I am responsible for my props, and those of other people's planes (a few with brand new props) which I fly from time to time. Since the 182 in the early days, I have not damaged a prop since....

If you think that you might be rough on prop blades, and it's worth the cost of the wear and tear, buy an MT prop, the blades can be repaired by replacement of damaged core, and leading edges.

[Heliian]

Check to see if there are published limits for nicks that don't require action. Those you can leave, but I always refer to the manual for any repairable damage.

Not only will blended repairs be safer than running around with damage, you'll be making the blade more efficient.

[shaynemarshallporath]

In the "good" ole days crusty old AMEs used to roll the nicks off the leading edge

[PilotDAR]

old AMEs used to roll the nicks off the leading edge

Okay, let's hope the young AME's are a lot brighter, as AC43.13-1B 8-73 says that doing that is not permissible.

Check to see if there are published limits for nicks that don't require action.

If the propeller manufacturer permits nicks [I'd be surprised] conform to their procedures. However, AC43.13-1B 8-73a states to "remove the metal around any ..... nicks......"

[shaynemarshallporath]

With the cost of fixed and CS prop blades and overhauls these days why doesn't the manufacturers come up with better LE protections ( I have tape on my C-150 and you can buy approved stuff but i am talking a better solution)

[Pacqing]

Maintainers on the West Coast used to have piston wrist pins to roll the nicks down. Not anymore as you can see by the toothpick blades on some of the float machines.

[photofly]

With the cost of fixed and CS prop blades and overhauls these days why doesn't the manufacturers come up with better LE protections

Um... why would you think?

[PilotDAR]

why doesn't the manufacturers come up with better LE protections

MT does, choose between stainless steel or nickel. I have the SS, one of my friends has the nickel. His prop has more than 400 water hours, and not a mark in it. And, the MT leading edges can be replaced if needed (as can a part of the blade).

As for a landplane, my experience has been that with care, leading edge protection is not required.

[ahramin]

My wood prop had a urethane leading edge, incredibly tough stuff.

[Heliian]

old AMEs used to roll the nicks off the leading edge

Okay, let's hope the young AME's are a lot brighter, as AC43.13-1B 8-73 says that doing that is not permissible.

Check to see if there are published limits for nicks that don't require action.

If the propeller manufacturer permits nicks [I'd be surprised] conform to their procedures. However, AC43.13-1B 8-73a states to "remove the metal around any ..... nicks......"

The old procedure of "burnishing" the metal blade with a heavy steel rod was found to create more problems in the end, it made it smooth but didn't relieve the stresses and could trap inclusions in the blade.

More complex prop systems will include limits for "negligible damage" limits published for continued operation. Usually in non critical areas.

[shaynemarshallporath]

The old procedure of "burnishing" the metal blade with a heavy steel rod was found to create more problems in the end, it made it smooth but didn't relieve the stresses and could trap inclusions in the blade.

Perhaps it was thought that minor imperfections ( not nicks) were smoothed out AND the metal was work hardened to act as a surface treatment ?

[PilotDAR]

Perhaps it was thought that minor imperfections ( not nicks) were smoothed out AND the metal was work hardened to act as a surface treatment ?

Perhaps, but such thinking would be counter to making a prop airworthy. AC43.13 is clear on how repairs should be done. Work hardening a prop leading edge would be a bad idea, that would promote cracking. Shot peening is sometimes done, but as a very controlled process. Smoothing out minor perfections by smearing high metal over low metal will do nothing to reduce the stress raisers in the bottom of the imperfections, and will hold moisture and corrosive elements.

Any imperfection should be thought of as a nick, until it's been repaired. Sure, some nicks are so tiny that there is no effect on the structure of the prop blade. If the prop manufacturer gives a negligible tolerance, use that. Any nick deep enough to be measured by simple means, is probably deep enough that it should be repaired. But a crack starts somewhere, and the bottom of a nick is more likely place than a smooth edge.

[photofly]

There was a prop repair shop that used sand blasting to clean props, not a process approved by the manufacturers, and an AD was issued to EDIT:overhaul every single prop they had ever touched...
https://hartzellprop.com/FAA/2005-14-11.pdf

Now that I try to find it again, I can't locate the document that referred to incorrect sand blasting. Did I imagine that, or is anyone else familiar?

[Heliian]

Now that I try to find it again, I can't locate the document that referred to incorrect sand blasting. Did I imagine that, or is anyone else familiar?

SCPS overhauled the Hartzell propeller where the blade failure occurred. There is evidence suggesting that
SCPS performed an improper repair procedure by welding or hot straightening on the blade that eventually
failed. As a result of the failure, the propeller lost approximately 10 inches from the blade tip and the aircraft
suffered substantial damage. The propeller only had 200 hours time-in-service (TIS) since the Southern
California Propeller Service overhaul during which the improper repair procedure was accomplished.
The six unairworthy propeller assemblies had safety critical problems including:
1) improperly drilled actuating pin holes and the unauthorized use of helicoils in the actuating pin holes, both
of which could lead to a higher stressed area and possible cracking with subsequent loss of propeller
blade pitch control,
2) corrosion pitting in a blade nut which could lead to a fatigue crack and subsequent blade failure,
3) blade retention clamps that were rusted and pitted in critical areas, which could lead to fatigue cracks or
failure and possible loss of the propeller blade,
4) bearing races that were rusted and pitted, which could lead to bearing seizure and loss of propeller blade
pitch control, and,
5) hub arms with corrosion pitting in the bearing retention radius and gouged, scratched and rusted in other
critical areas, which could lead to fatigue cracks and subsequent hub failure, blade loss, and loss of
aircraft control.

From the special notice quoted in the a.d.

[edmanster]

Ran a large Flight School Maint - mid nineties ..
Consider informing the pilots & instructors (also maint crew) about techniques to avoid such damage ..
- Inspect ramp areas where runups are conducted for debris / sweep off if possible / have airport Auth sweep it
- Avoid prolonged full power run-ups
- Rolling runups on gravel / make use grassy areas
- paint blades - so abrasion is more evident to the flight crew ..
(so they do not become complacent)
- have instructors report prop chips to maintenance - this will encourage management's concern.
- have a "toothpick" prop on display at ground school. (& explain why its a bad thing!)
- little more discussion in early training about picking up rocks with props ..
- More care & consideration at full power !

.. reminds me of old story ..
In mid-nineties / Air BC flew BAE-146 & had 1 parked on ramp overnight.
Turbo-prop in front of the 4 Engine 146 decided to conduct a full power runup.
Picked up all the ramp debris & sent it into the intakes of the 146.
needless to say .. very expensive day for the 2 aircraft owners ..

[rigpiggy]

why doesn't the manufacturers come up with better LE protections

MT does, choose between stainless steel or nickel. I have the SS, one of my friends has the nickel. His prop has more than 400 water hours, and not a mark in it. And, the MT leading edges can be replaced if needed (as can a part of the blade).

As for a landplane, my experience has been that with care, leading edge protection is not required.

MTs are garbage, I wouldn’t put them on any of my planes. Repaired every blade (8) 22k and 3 months later. After purchase support sucks